Abstract

Neutron diffractionanalysis of the cubic phase of CaC2 has revealed the characteristics of the hindering potential for rotation of the C2 group, i.e., the body diagonal axes being the easiest direction for the C2 random orientation, the face diagonals being the next easiest and the cube axes being by far the hardest. A further refinement on the published neutron data of cubic KCN indicates, on the contrary to the previous analyses, a clear distinction among various orientational modes of the CN group and consequently the rotational hindering potential analogous to the CaC2 case.